This invention relates to a driving apparatus for a gas discharge display panel for displaying characters and figures by use of gas discharge.
A gas discharge display panel is already commonly known from the disclosure of, for example, a paper entitled "A NEW dc PDP WITH LOW VOLTAGE DRIVE AND HIGH RESOLUTION", Amano et al, Proceedings of the SID, Vol. 23/3, 1982, pp. 169-174. This panel has, however, been disadvantageous in that it has a structure which requires many driving circuits.
A patent application relating to a display panel which solves the problem is now pending (Ser. No. 684,298) and is assigned to the same assignee as the present invention. This new type panel comprises, as shown in FIG. 1, a plurality of parallel cathodes 20 arranged on a substrate 10 and connected by polyphase wiring 21, a plurality of parallel barriers 30 disposed on the cathodes 20 in such a manner as to cross the cathodes at right angles, and a plurality of parallel anodes 50 disposed on a transparent face plate 40 in parallel with the barriers 30. Flourescent areas 60 are also disposed on the face plate 40 for color display. The substrate 10 and the face plate 40 thus prepared are then put together to form a display panel.
FIG. 2 shows the connection between electrodes and terminals of the panel. The cathodes 20 (K1, K2, K3 . . . KN) are connected in four phases to respective cathode terminals K.phi.1-K.phi.4. The anode 50 is connected to an anode terminal A through a resistor r. A reset electrode RE for the panel is disposed on the side of the parallel cathodes 20. A pair of keep-alive electrodes are disposed adjacent to the reset electrode RE to ensure reliable operation of the panel.
FIG. 3 shows pulses that are applied to each electrode. A reset pulse (width=tR, amplitude=VR, period=T) is applied to terminal R of FIG. 2 which is connected to the reset electrode RE. Cathode pulses (width=tK, amplitude=VK, period=4tK) are applied to the cathode terminals K.phi.1-K.phi.4 in time sequence, the phases of which are shifted a period tK with respect to each other. Anode pulses which are composed of auxiliary discharge pulses (width=tS', amplitude=VA, period=tK) and display pulses (width=tD' amplitude=VA, period=tK) are applied to the anode terminal A in synchronism with the cathode pulses, as shown in FIG. 3. The auxiliary discharge pulses are continuous scanning pulses for self-scanning driving and the display pulses correspond to an information display signal.
As a result of its structure, this new type panel has the advantage of reducing driving circuits.
However, the pulse width tS' of the auxiliary discharge pulses must be kept at a larger size when the panel is driven with the pulses as shown in FIG. 3, because the panel can not operate stably with small auxiliary discharge pulses. Therefore, the ratio (BD/BS) of display luminance BD to the back-light BS, that is, a contrast ratio (BD/BS.alpha.tD'/tS') drops eventually and visibility also drops.